There continues to be a need for removal of hydrocarbon contamination both in soil and in ground water. "Pump and treat" or pumping ground water to the surface and treating has been shown to relatively slow and expensive. In situ air sparging has been shown to require extended periods of time for sufficient removal. The objectives of this invention include in situ removal from both the underlying ground water and the soil above in minimum time with lowest overall cost.
There appears to be a specific need for removal of hydrocarbons such as gasoline from the soil and in some cases the groundwater below valuable real estate sites such as filling stations, railyards etc. . . . .
The major objective of this invention is to provide a relatively low cost time predictable method for in situ hydrocarbon removal from groundwater and soil.
The closest prior art we have found is U.S. Pat. No.4,832,122 to Corey et al issued May 23,1989. Our invention is similar in that we plan to use multiple pipes installed using horizontal drilling techniques for sparging below the contaminated zone. We differ significantly as follows
a) we use a multiplicity of perforated vertical pipes to collect the sparger gas and the hydrocarbon associated therewith, PA1 b) we use a multiplicity of perforated vertical wash pipes spaced between the perforated vertical collector pipes to wash the soil to free hydrocarbons before they reach the groundwater; hydrocarbons and wash water or wash solution entering the collector pipes will be hydrocarbon stripped as the mixture falls downward,or may be entrained to the surface for normal treatment either by the sparging gas or by an auxiliary small pipe carrying an entrainment gas inserted in the collector, PA1 c) we use carbon dioxide as the sparging gas; PA1 d) we determine approximate quantity of the contaminant by drilling and sampling; PA1 e) we monitor the removal of the hydrocarbon and flow rate of the influent carbon dioxide or stripping gas and from this data may vary flow for maximum economic efficiency; PA1 f) we pull a slight vacuum continuously on the collection header to speed the remediation; PA1 e) we may calculate probable clean -up time from a semilog graph of effluent hydrocarbon contamination versus time. PA1 g) with excessive clean up times indicated we may augment the recovery system. PA1 a) determining the depth and extent of the contaminated zone by drilling and sampling, PA1 b) installing perforated pipes horizontally below the contaminated zone and in the ground water table; PA1 c)installing a matrix of vertical perforated collector pipes on about eight foot centers or further apart dependant upon the geology of the zone, from the ground surface to just above the watertable or groundwater; PA1 d) installing a matrix of vertical perforated wash pipes between said collector pipes; PA1 e) injecting an environmentally innocuous wash solution such as water, water plus carbon dioxide, water plus an inorganic salt such as sodium sulfate,water plus detergent etc. to displace hydrocarbon contaminants to flow toward and into said collector pipes; PA1 f) sparging a stripping gas such as air, nitrogen, or carbon dioxide with carbon dioxide being preferable through said horizontal sparging pipes, PA1 g) headering together the above ground ends of the collector pipes and pulling a slight vacuum in the collector pipes using a pump such as a Roots-Connersville blower, PA1 h) discharging the blower through a water knock out pot, and through a hydrocarbon removal system such as an activated charcoal bed and recycling back to continue sparging the formation, PA1 i) continuing the operation with sampling of the gas in the collector header to determine indicated clean-up, PA1 j) determining site clean up by sampling and analysis of the groundwater and the soil; PA1 k)pumping oil digesting microbes through the wash tubes for final clean up of the hydrocarbon contaminant.